javascript - What does $scope.$apply() do?

Question

I've been using $scope.$apply() to update the bindings for my models when I receive data through websockets in my Angular apps and it works. But what does it actually do and why does it need to be called to achieve the update?

Answer 1

If you call $apply the code provided will be executed in angular-context which you can make use of what angular provides.

From the link:

Angular modifies the normal JavaScript flow by providing its own event processing loop. This splits the JavaScript into classical and Angular execution context. Only operations which are applied in Angular execution context will benefit from Angular data-binding, exception handling, property watching, etc...

You can also use $apply() to enter Angular execution context from JavaScript. Keep in mind that in most places (controllers, services) $apply has already been called for you by the directive which is handling the event. An explicit call to $apply is needed only when implementing custom event callbacks, or when working with third-party library callbacks.